Water heater apparatus



Aug. 18, 1953 K. L. WOODMAN WATER HEATER APPARATUS Filed Feb. 8, 1952Insulating cooflnq FIG v A .INVENTOR KENNETH L.WOODMAN WITNES ES:

ATTORN EY Patented Aug. 18, 1953 UNITED STATES PATENT OFFICE WATERHEATER APPARATUS Kenneth L. Woodman, Mansfield, Ohio, assignor toWestinghouse Electric Corporation, East Pittsburgh, Pa., a corporation.of Pennsylvania Application February 8, 1952, Serial No. 270,540

4 Claims. 1

This invention relates to electrically heated water heaters,particularly electrical water heaters having an immersion heating unitmounted therein and an anode for protecting the walls of the tank fromcorrosion.

It is an object of the invention to provide a water heater in which theanode is more efficiently utilized to protect the tank walls fromcorrosion.

It is a further object of the invention to provide, in a water heaterhaving an anode for protecting the tank, a sheathed heating unit of theimmersion type which will not affect the protective current to the tankwall.

A still further object is to provide a water heater having an anode inwhich the protective current from the anode is utilized in a mostefficient manner to protect the tank, and currents from the anode to theimmersion heating unit are reduced to a minimum.

I have found that, in water heaters having an immersion heating unit forheating the Water and an anode for protecting the walls of the tank fromthe effects of electrolysis, current from the anode, in the vicinity ofthe immersion heating unit, is attracted to the latterinstead of to thewalls of the tank. This effect reduces the protective action of theanode on the tank wall in the vicinity of the heating unit.

In accordance with the above objects, I propose coating the entiresurface of the immersion heating unit sheath exposed to contact with thewater, with an electrical insulating coating. This coating may be in thenature of a varnish which may be applied to the external surface of thesheath by spraying, dipping orbrushing. The

varnish may be of any well-known type, such as, for example, thosevarnishes now on the market under the following trade names: Micarta,Permolite or Heresite. With such a coating on the immersion heatingunit, current from the anode through the heating unit is substantiallyeliminated. Instead, the current which has been heretofore divertedthrough the heating unit will flow to the tank wall in the area of theheating unit and serve to protect the former in the same manner as theother portions of the tank walls.

The above and the objects are effected by my invention as will beapparent from the following description taken in connection with theaccompanying drawings, forming a part of this application, in which:

Fig. I is a vertical section of a water heater having my inventionincorporated therein;

Fig. 2 isa section taken on line II-II of Fig. l; and

Fig. 3 is a section of the heating unit, on a muchlarger scale, taken online III-III of Fig. 1.

Referring to the drawings, especially Fig. 1, there is shown a waterheater, generally designated l0, having a tank 12 comprising a tubularvertical wall [4 and upper and lower end walls It and t8, respectively.The tank i2 is provided with an infiuent Water pipe 20- which isreceived in threaded engagement with an opening in the lower end wall[8. The upper end wall It is pro-- vided with an efiluent water pipe 24which servesto carry off the heated water in a manner which is wellunderstood. The upper end wall If; isfurther provided with a centrallydisposed threaded opening through which is inserted an anode rod 26-.The anode 26 extends downwardly into the tank to within a short distanceof the lower end wall It and is fastened at its upper end to a supportmember 28 which is screwthreaded to the upper end wall Hi. The anode 26may be of the sacrificial type, made of any metal which is higher in theelectro chemical series than the material of which the tank walls aremade, and is in good electrical contact with the end wall l6 through thesupport member 28. For example, if the tank walls are made of steel, theanode may be composed of magnesium, zinc, aluminum or other similarmetals. As is well understood in the art, current will flow from theanode 26, through the water in the tank to the inner surfaces of thetank Walls M, It and 18, respectively, thereby preventing corrosion ofthe tank wall by electrolysis.

The tank wall I4 is provided with an opening 32 through which extends asheathed immersion heating unit 34, which is preferably though not.necessarily of substantially hairpin shape in vertical aspect and curvedin horizontal aspect, as shown in Fig. 2. The heating unit 34' isfastened to the tank wall adjacent the opening 3-2 by a mounting plate36, which plate also serves to close the opening 32.

As best shown in Fig. 3, the sheathed heating unit 34' comprises ahelically wound resistor wire Ml disposed centrally of a metallictubular sheath 42 and insulatedly spaced therefrom by a highly compactedrefractory powder 44', as is well understood' in the art. Thus, theresistor MI is iii-- sulated from the sheath 42 and is sealed againstentrance of water contained in the tank. The

. sheath 42 may be made of any desirable metal;

anode and the sheathed heating unit 34 is less than the distance betweenthe anode and the tubular wall H of the tank. Thus, as thus fardescribed, current from the anode, seeking the shortest route to ground,will pass through the sheath 42 of the heating unit in preference to thetank wall in the area adjacent the heater, minimizing the desiredprotective action of the anode on the tank wall. To minimize thediversion of current described, the sheath 42 is coated with anelectrical insulating varnish 46 which will withstand the effects of hotwater. The varnish 46 may be of any well-known type such as, forexample, those varnishes now appearing on the market under the followingtrade names: Micarta, Permolite, Heresite, etc.

The heating unit 34, although in direct contact with the water in thetank, is insulated against electrical contact therewith by theinsulating varnish 46. Although heat given off by the resistor 40 isreadily transmitted to the water in the tank, current from the anodecannot flow through the sheath 42 because of the insulation providedthereon by the varnish 46. In actual production there may be someinstances where the insulating coating 46 is broken by minute pinholes.However, current flowing through such pinholes to the sheath would be sominute that it is negligible. It will now be seen that the current fromthe anode which had heretofore been diverted from the tank wall ispermitted to flow entirely to the tank wall, thereby providing theutmost protection to the inner surface of the tank walls. Since thecurrent from a sacrificial anode is a limited one, this effect isadvantageous in imparting a longer useful life to the tank.

Although the invention has been described in connection with a waterheater having a steel tank, it is also advantageous when utilized with atank having an inner protective lining composed of zinc or glass of thetype now commonly used. Although, in theory, tanks having a protectiveinner surface of the above-mentioned substances are immune toelectrolytic corrosion, in actual practice it has been found that asmooth unbroken surface in the coating is very difficult to attain. Forexample, in zinc-lined tanks, bare spots or thin spots formed in thezinc coating during manufacture of the tank render the tank wallvulnerable at these points to localized electrolytic currents. Inglass-lined tanks, the surface is often broken by small pinholes orcracks which create vulnerable spots in the tank wall. In view of theabove, water heaters are usually provided with anodes, regardless ofwhether the tank is unlined or lined with a protective coating.

Also, although the invention has been described in connection with awater heater having an anode of the sacrificial type, it is not limitedthereto and may be utilized with a water heater having an anode of thepermanent type. Permanent type anodes are well known in the art and areconnected to a low voltage current supply.

Regardless of the type of anode employed, more complete protection maybe obtained by coating the immersion heater with the insulating coatingheretofore described. The insulating coating will not waste away sinceit is not affected by the action of the anode or of the water containedin the tank. Hence, the increased efficiency imparted to the anode issubstantially a permanent one and is limited only by the life of theanode and of the immersion heating unit.

While I have shown my invention in but one form, it will be obvious tothose skilled in the art 4 that it is not so limited, but is susceptibleof various changes and modifications without departing from the spiritthereof.

What I claim is:

1. An immersion heating unit for a water heater, comprising a metallictubular sheath, a heating element disposed within said sheath,electrical insulating material spacing said heating element from saidsheath, and an electrical insulating coating on the outer surface ofsaid sheath, saidinsulating coating being resistant to hot water andserving to electrically insulate the outer surface of said sheath.

2. In combination, a water heater comprising a tank, an anode disposedwithin said tank, an immersion heating unit passing through an openingin said tank and being fastened to the wall of the tank, said heaterhaving a metallic tubular sheath, a heating element disposed within saidsheath and electrically insulated from the sheath, and an electricallyinsulating coating disposed on the outer surface of said sheath andserving to electrically insulate the sheath from water contained in saidtank.

3. In combination, a water heater comprising a tank having a tubularwall and end walls, an anode disposed in said tank, said anode beingfastened at one end to said end wall, said tubular wall having anopening, an immersion heating unit passing through said opening andhaving a mounting plate for closing said opening, said heating unithaving a tubular sheath, a heating element disposed within said sheathand electrically insulated therefrom, and an electrically insulatingcoating on said sheath, said coating covering that portion of saidsheath disposed within said tank and serving to electrically insulatethe sheath from water within the tank, whereby protective currentflowing from the anode to the tank wall will not be diverted throughsaid sheath.

4. In combination, a water heater comprising a metallic tank having atubular wall and end walls, an anode disposed in said tank, said anodecomprising a member composed of a metal higher in the electro-chemicalseries than the material comprising said tank walls, said anode beingfastened to one of said walls in good electrical contact therewith,whereby an electrical circuit is set up from said anode to said tankwalls to protect the interior surface of said tank walls from corrosion,said tubular wall having an opening, an immersion heating unit passingthrough said opening and having a mounting plate for closing saidopening, said heating unit having a metallic tubular sheath, a heatingelement disposed within said sheath and electrically insulatedtherefrom, an electrically insulating coating on said sheath, saidcoating covering that portion of said sheath disposed within said tankand serving to electrically insulate the sheath from water within thetank, whereby protective current flowing from the anode to the tankwalls will not be diverted to said sheath.

KENNETH L. WOODMAN.

References Cited in the file of this patent UNITED STATES PATENTS Number

